openat

9cc8199d · Nickolai Zeldovich · bbb74797 · 9cc8199d · 9cc8199d · 9cc8199d
--- a/include/fcntl.h
+++ b/include/fcntl.h
@@ -2,3 +2,5 @@
 #define O_WRONLY  0x001
 #define O_RDWR    0x002
 #define O_CREATE  0x200
+
+#define AT_FDCWD  -100
--- a/include/kern_c.h
+++ b/include/kern_c.h
@@ -31,7 +31,7 @@ long sys_kill(int);
 long sys_link(const char*, const char*);
 long sys_mkdir(const char*);
 long sys_mknod(const char*, int, int);
-long sys_open(const char*, int);
+long sys_openat(int, const char*, int);
 long sys_pipe(int*);
 long sys_read(int, char*, int);
 long sys_sbrk(int);

--- a/include/kernel.hh
+++ b/include/kernel.hh
@@ -99,7 +99,7 @@ int             filewrite(struct file*, char*, int n);
 int             namecmp(const char*, const char*);
 struct inode*   dirlookup(struct inode*, char*);
 struct inode*   ialloc(u32, short);
-struct inode*   namei(const char*);
+struct inode*   namei(inode *cwd, const char*);
 void            iput(struct inode*);
 struct inode*   iget(u32 dev, u32 inum);
 void            ilock(struct inode*, int writer);
@@ -110,7 +110,7 @@ int             readi(struct inode*, char*, u32, u32);
 void            stati(struct inode*, struct stat*);
 int             writei(struct inode*, char*, u32, u32);
 struct inode*   idup(struct inode*);
-struct inode*   nameiparent(const char*, char*);
+struct inode*   nameiparent(inode *cwd, const char*, char*);
 int             dirlink(struct inode*, const char*, u32);
 void            dir_init(struct inode *dp);
 void	        dir_flush(struct inode *dp);

--- a/include/syscall.h
+++ b/include/syscall.h
@@ -8,7 +8,7 @@
 #define SYS_close   7
 #define SYS_kill    8
 #define SYS_exec    9
-#define SYS_open   10
+#define SYS_openat 10
 #define SYS_mknod  11
 #define SYS_unlink 12
 #define SYS_fstat  13

--- a/include/user.h
+++ b/include/user.h
@@ -30,6 +30,7 @@ void halt(void);
 ssize_t pread(int, void*, size_t, off_t);
 int async(int, size_t, off_t, u32, u32);
 int script(void *addr, u64 len, u64 chunk);
+int openat(int dirfd, const char *pathname, int omode);

 // ulib.c
 int stat(char*, struct stat*);

--- a/kernel/bootdata.c
+++ b/kernel/bootdata.c
@@ -41,7 +41,7 @@ long (*syscalls[])(u64, u64, u64, u64, u64) = {
  SYSCALL(link),
  SYSCALL(mkdir),
  SYSCALL(mknod),
-  SYSCALL(open),
+  SYSCALL(openat),
  SYSCALL(pipe),
  SYSCALL(read),
  SYSCALL(sbrk),

--- a/kernel/exec.cc
+++ b/kernel/exec.cc
@@ -153,7 +153,7 @@ exec(const char *path, char **argv)
  struct vmap *oldvmap;

  prof_start(exec_prof);
-  if((ip = namei(path)) == 0)
+  if((ip = namei(myproc()->cwd, path)) == 0)
    return -1;

  gc_begin_epoch();

--- a/kernel/fs.cc
+++ b/kernel/fs.cc
@@ -745,7 +745,7 @@ skipelem(const char **rpath, char *name)
 // If parent != 0, return the inode for the parent and copy the final
 // path element into name, which must have room for DIRSIZ bytes.
 static struct inode*
-namex(const char *path, int nameiparent, char *name)
+namex(inode *cwd, const char *path, int nameiparent, char *name)
 {
  struct inode *ip, *next;
  int r;
@@ -754,7 +754,7 @@ namex(const char *path, int nameiparent, char *name)
  if(*path == '/') 
    ip = iget(ROOTDEV, ROOTINO);
  else
-    ip = idup(myproc()->cwd);
+    ip = idup(cwd);

  while((r = skipelem(&path, name)) == 1){
    next = 0;
@@ -790,17 +790,17 @@ namex(const char *path, int nameiparent, char *name)
 }

 struct inode*
-namei(const char *path)
+namei(inode *cwd, const char *path)
 {
  char name[DIRSIZ];
-  struct inode *r = namex(path, 0, name);
+  struct inode *r = namex(cwd, path, 0, name);
  //cprintf("namei: %s -> %x (%d)\n", path, r, r?r->inum:0);
  return r;
 }

 struct inode*
-nameiparent(const char *path, char *name)
+nameiparent(inode *cwd, const char *path, char *name)
 {
-  return namex(path, 1, name);
+  return namex(cwd, path, 1, name);
 }

--- a/kernel/proc.cc
+++ b/kernel/proc.cc
@@ -101,7 +101,7 @@ forkret(void)
  // in which to call cv_sleep().
  if(myproc()->cwd == nullptr) {
    mtstart(forkret, myproc());
-    myproc()->cwd = namei("/");
+    myproc()->cwd = namei(myproc()->cwd, "/");
    mtstop(myproc());
  }


--- a/kernel/sysfile.cc
+++ b/kernel/sysfile.cc
@@ -132,7 +132,7 @@ sys_link(const char *old, const char *newn)

  if(argcheckstr(old) < 0 || argcheckstr(newn) < 0)
    return -1;
-  if((ip = namei(old)) == 0)
+  if((ip = namei(myproc()->cwd, old)) == 0)
    return -1;
  ilock(ip, 1);
  if(ip->type == T_DIR){
@@ -143,7 +143,7 @@ sys_link(const char *old, const char *newn)
  iupdate(ip);
  iunlock(ip);

-  if((dp = nameiparent(newn, name)) == 0)
+  if((dp = nameiparent(myproc()->cwd, newn, name)) == 0)
    goto bad;
  if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0)
    goto bad;
@@ -185,7 +185,7 @@ sys_unlink(const char *path)

  if(argcheckstr(path) < 0)
    return -1;
-  if((dp = nameiparent(path, name)) == 0)
+  if((dp = nameiparent(myproc()->cwd, path, name)) == 0)
    return -1;
  if(dp->type != T_DIR)
    panic("sys_unlink");
@@ -234,13 +234,13 @@ sys_unlink(const char *path)
 }

 static struct inode*
-create(const char *path, short type, short major, short minor)
+create(inode *cwd, const char *path, short type, short major, short minor)
 {
  struct inode *ip, *dp;
  char name[DIRSIZ];

 retry:
-  if((dp = nameiparent(path, name)) == 0)
+  if((dp = nameiparent(cwd, path, name)) == 0)
    return 0;
  if(dp->type != T_DIR)
    panic("create");
@@ -284,20 +284,32 @@ create(const char *path, short type, short major, short minor)
 }

 long
-sys_open(const char *path, int omode)
+sys_openat(int dirfd, const char *path, int omode)
 {
  int fd;
  struct file *f;
  struct inode *ip;
+  struct inode *cwd;
+
+  if (dirfd == AT_FDCWD) {
+    cwd = myproc()->cwd;
+  } else if (dirfd < 0 || dirfd >= NOFILE) {
+    return -1;
+  } else {
+    struct file *fdir = myproc()->ofile[dirfd];
+    if (fdir->type != file::FD_INODE)
+      return -1;
+    cwd = fdir->ip;
+  }

  if(argcheckstr(path) < 0)
    return -1;
  if(omode & O_CREATE){
-    if((ip = create(path, T_FILE, 0, 0)) == 0)
+    if((ip = create(cwd, path, T_FILE, 0, 0)) == 0)
      return -1;
  } else {
 retry:
-    if((ip = namei(path)) == 0)
+    if((ip = namei(cwd, path)) == 0)
      return -1;
    ilock(ip, 0);
    if(ip->type == 0) {
@@ -335,7 +347,7 @@ sys_mkdir(const char *path)
 {
  struct inode *ip;

-  if(argcheckstr(path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0)
+  if(argcheckstr(path) < 0 || (ip = create(myproc()->cwd, path, T_DIR, 0, 0)) == 0)
    return -1;
  iunlockput(ip);
  return 0;
@@ -348,7 +360,7 @@ sys_mknod(const char *path, int major, int minor)
  int len;
  
  if((len=argcheckstr(path)) < 0 ||
-     (ip = create(path, T_DEV, major, minor)) == 0)
+     (ip = create(myproc()->cwd, path, T_DEV, major, minor)) == 0)
    return -1;
  iunlockput(ip);
  return 0;
@@ -359,7 +371,7 @@ sys_chdir(const char *path)
 {
  struct inode *ip;

-  if(argcheckstr(path) < 0 || (ip = namei(path)) == 0)
+  if(argcheckstr(path) < 0 || (ip = namei(myproc()->cwd, path)) == 0)
    return -1;
  ilock(ip, 0);
  if(ip->type != T_DIR){

--- a/lib/ulib.c
+++ b/lib/ulib.c
@@ -130,3 +130,9 @@ memmove(void *vdst, const void *vsrc, int n)
    *dst++ = *src++;
  return vdst;
 }
+
+int
+open(const char *path, int omode)
+{
+  return openat(AT_FDCWD, path, omode);
+}
--- a/lib/usys.S
+++ b/lib/usys.S
@@ -25,7 +25,7 @@ SYSCALL(write)
 SYSCALL(close)
 SYSCALL(kill)
 SYSCALL_INT(exec)
-SYSCALL(open)
+SYSCALL(openat)
 SYSCALL(mknod)
 SYSCALL(unlink)
 SYSCALL(fstat)